this invention relates to the preparation of organopolysiloxane polymers and more particularily to a process for preparing organopolysiloxane polymers by reacting halosilanes with organopolysiloxanes in the presence of activated charcoal.
Heretofore it was known that chlorosilanes and organosiloxanes undergo equilibrium reactions to form a mixture of compounds conprising some unreacted halosilanes and organopolysiloxanes. These reactions have been conducted in the presence of catalysts such as hydrogen halides, inorganic acids, Lewis acids, such as ferric chloride, alkali metal halides, inert polar solvents, amines, amine salts, ammonium salts and phosphorous compounds.
The equilibrium reactions of halogenosilanes with organosiloxanes in the presence of a catalyst such as a hydrogen halide or a mixture of a hydrogen halide or ferric chloride is well known as evidenced by the disclosure of U.S. Pat. No. 2,421,653 to Sauer.
Also U.S. Pat. No. 3,065,252 to Brown et al describes the reaction of halogenosilanes or halogenosiloxanes with organosiloxanes in the presence of catalysts, such as aminoalkyl-substituted organosilicon compounds, salts of monocarboxylic acids and aminoalkyl-substituted organosilicon compounds.
Brown et al describe in U.S. Pat. No. 3,101,361 the interaction of a silane or silicone containing at least one halogenated silicon atom per molecule with a siloxane in the presence of catalysts such as aliphatic hydrocarbon amines, salts of hydrogen halides and said amines and salts of monocarboxylic acid and aliphatic hydrocarbon amines and an organic solvent.
Also in U.S. Pat. No. 3,162,662 Brown et al describe a process for preparing linear chlorosiloxanes by interacting a halogenosilicon compound with cyclotrisiloxane in the presence of catalysts such as amines, amine salts of monocarboxylic acids, amine salts of monocarboxylic acids and quaternary ammonium halides, amides, alkali metal halides and ammonium salts of monocarboxylic acids and inert organic solvents.
Wegehaupt et al disclose in U.S. Pat. No. 3,549,680 a method for preparing organohalogenosilicon compounds by reacting halogenosilicon compounds with organosiloxanes free of halogen bonded silicon in the presence of phosphonitrile halides and certain organonitrogen derivatives of phosphorous acid or phosphoric acid.
Bennett describes in U.S. Pat. Nos. 3,642,851 and 3,686,253 a process for preparing linear halosiloxane polymers through the redistribution of halosiloxanes or a halosiloxane with cyclotrisiloxane or cyclotetrasiloxane in the presence of phosphine oxides or amine oxides.
U.S. Pat. No. 3,646,088 to Bakassian et al, discloses conducting the redistribution reaction between a siloxane and a chlorosilane in the presence of hexalkylphosphotriamide.
In comparison with the processes described above for conducting the equilibration reaction between organosiloxanes and chlorosilanes, the process of this invention has certain advantages. For example, it avoids cleavage of the SiC-bonded organic groups, such as phenyl, vinyl or gamma-chloropropyl groups and/or avoids the formation of decomposition products which have a noxious odor. Moreover, it does not require cyclotrisiloxanes which are relatively difficult to acquire, nor does it require considerable amounts of inert polar solvents which are expensive and often difficult to recover. Furthermore, the catalyst need not be separated from the reaction product nor is it necessary to neutralize the catalyst in the reaction product. Another advantage of the process of this invention is that there is a reduction in the reaction time with increased yields of product.